1. Field of the Invention
This invent ion relates to an improvement in a frame assembly for a mold for expansion molding, particularly for a mold for molding of expanded polystyrene.
2. Statement of Prior Art
The mold for molding of expanded polystyrene to be mounted on an automatic molding machine is generally composed of a set of a concave stationary side part (cavity part) and a convex moving side part (core part), which are disposed opposedly, having respective frames fitted at the opposite sides thereof with backplates, to form a steam chamber inside.
One example of conventional frames for a mold of the kind stated above is shown in FIG. 5 in which a plurality of plates (11) (12) are cast from aluminum alloy and united together by welding to form a square frame. Another example includes a one-piece frame fashioned by casting of aluminum alloy.
However, manufacturing the one-piece frame made of cast aluminum alloy and the frame united by welding of cast plates stated above are problematic in that the casting process is complicated, expensive, and time consuming. In altering the production of moldings where the shape of the moldings and the cavity number per one mold are changed, respective frames suited to the respective molds have to be provided, which is extremely uneconomical. Furthermore, the existing frames are prone to cause diminution of strength attended by blemish of castings or deterioration of castings upon welding, and consequently, there is a problem in long-term use.